To mold an optical element by injection molding of a synthetic resin, a mold of a metallic material such as steel has been used in the conventional art. In recent years, the optical element is required to provide high precision on the order of a micron or below due to the trend towards microstructure and the high precision of optical products. The conventional mold has failed to meet the requirements for such high precision transferability. To meet the requirements for molding such a high-precision optical element, Patent Document 1 discloses a mold for molding an optical element wherein a heat insulating layer and surface treatment layer are formed on the surface of a stainless steel core mold.
According to the mold for molding the optical element described in this document, a ceramic material is sprayed on the surface of the core mold, and a heat insulating layer is formed integrally with the mold base material. A nonferrous metal material is electroless-plated on the heat insulating layer. This procedure is said to allow a high-precision metallic structure to be formed on the surface treatment layer, whereby a molded product having minimized geometric error is produced.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-96335